A hydrogen generating apparatus including a reformer for generating a hydrogen-containing gas through a steam reforming reaction using as a material gas a hydrocarbon based gas such as a natural gas or LPG, is suitably used to generate the hydrogen-containing gas which is supplied to a fuel cell.
In a method of stopping the hydrogen generating apparatus, the hydrogen generating apparatus is sealed under the state the material gas is filled therein. There is proposed a hydrogen generating apparatus in which in order to prevent a negative pressure in the reformer which is generated according to a decrease in a temperature in the interior of the hydrogen generating apparatus after the sealing, the material gas is fed after a specified time to maintain the interior at a positive pressure (e.g., see patent document 1).
There is also disclosed that a plurality of valves are used to seal a space of a fuel cell system including a hydrogen generating apparatus and a material gas is fed to the hydrogen generating apparatus based on its internal pressure or its internal temperature to prevent generation of a negative pressure in the hydrogen generating apparatus, thereby maintaining the interior at a positive pressure after the hydrogen generating apparatus has become a stop state (see Patent document 2).    Patent document 1: Japanese Laid-Open Patent Application Publication: No. 2003-229156    Patent document 2: Japanese Laid-Open Patent Application Publication: No. 2005-44653